White smoke usually means coolant is making it's way into the combustion chamber(s). Pull the spark plugs and check which one looks unnaturally clean and it'll give you a hint on where the core issue is located. This would definitely explain the white smoke and coolant loss, the subsequent loss of power and overheating. Also check your thermostat. If it's seized up it will prevent adequate coolant flow and won't give the engine enough of a chance to direct coolant to the radiator for the cooling cycle to be effective. If you need a new head, get a non-jet valve if possible. Disabling or deleting the jet valves is a band aid fix IMO.

*Added thought - consider using an electric thermo fan to replace the water pump driven clutch fan. Way more effective when it comes to engine cooling.